/**
 * Copyright 2013-2020 the original author or authors from the JHipster project.
 *
 * This file is part of the JHipster project, see http://www.jhipster.tech/
 * for more information.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

module.exports = {
    camelCase,
    upperFirst,
    lowerFirst,
};

function camelCase(string) {
    checkStringIsValid(string);
    if (string === '') {
        return string;
    }
    const [firstLetter, ...rest] = string.replace(/[\W_]/g, '');
    return `${firstLetter.toLowerCase()}${rest.join('')}`;
}

function upperFirst(string) {
    checkStringIsValid(string);
    if (string === '') {
        return string;
    }
    const [firstLetter, ...rest] = string;
    return `${firstLetter.toUpperCase()}${rest.join('')}`;
}

function lowerFirst(string) {
    checkStringIsValid(string);
    if (string === '') {
        return string;
    }
    const [firstLetter, ...rest] = string;
    return `${firstLetter.toLowerCase()}${rest.join('')}`;
}

function checkStringIsValid(string) {
    if (string === undefined || string === null) {
        throw new Error('The passed string cannot be nil.');
    }
}
